Fix issue where CREAT flag was not properly passing mode (#23)

* Pass on CREAT mode propertly in open interceptors

* Add unit tests

* Remove two unneccessary bits

* Fix fcntl

Author: cjappl

compiler-rt/lib/radsan/radsan_interceptors.cpp

@@ -52,6 +52,7 @@ INTERCEPTOR(int, open, const char *path, int oflag, ...) {
   // TODO Establish whether we should intercept here if the flag contains
   // O_NONBLOCK
   __radsan::ExpectNotRealtime("open");
+
   va_list args;
   va_start(args, oflag);
   const mode_t mode = va_arg(args, int);
@@ -65,6 +66,7 @@ INTERCEPTOR(int, openat, int fd, const char *path, int oflag, ...) {
   // TODO Establish whether we should intercept here if the flag contains
   // O_NONBLOCK
   __radsan::ExpectNotRealtime("openat");
+
   va_list args;
   va_start(args, oflag);
   mode_t mode = va_arg(args, int);
@@ -84,22 +86,13 @@ INTERCEPTOR(int, creat, const char *path, mode_t mode) {
 
 INTERCEPTOR(int, fcntl, int filedes, int cmd, ...) {
   __radsan::ExpectNotRealtime("fcntl");
+
   va_list args;
   va_start(args, cmd);
-
-  // Following precedent here. The linux source (fcntl.c, do_fcntl) accepts the
-  // final argument in a variable that will hold the largest of the possible
-  // argument types (pointers and ints are typical in fcntl) It is then assumed
-  // that the implementation of fcntl will cast it properly depending on cmd.
-  //
-  // This is also similar to what is done in
-  // sanitizer_common/sanitizer_common_syscalls.inc
-  const unsigned long arg = va_arg(args, unsigned long);
-  int result = REAL(fcntl)(filedes, cmd, arg);
-
+  void *arg = va_arg(args, void *);
   va_end(args);
 
-  return result;
+  return fcntl(filedes, cmd, arg);
 }
 
 INTERCEPTOR(int, close, int filedes) {

compiler-rt/lib/radsan/tests/radsan_test_interceptors.cpp

@@ -204,6 +204,22 @@ TEST(TestRadsanInterceptors, OpenatDiesWhenRealtime) {
   std::remove(TemporaryFilePath());
 }
 
+TEST(TestRadsanInterceptors, openCreatesFileWithProperMode) {
+  const int mode = S_IRGRP | S_IROTH | S_IRUSR | S_IWUSR;
+
+  const int fd = open(TemporaryFilePath(), O_CREAT | O_WRONLY, mode);
+  ASSERT_THAT(fd, Ne(-1));
+  close(fd);
+
+  struct stat st;
+  ASSERT_THAT(stat(TemporaryFilePath(), &st), Eq(0));
+
+  // Mask st_mode to get permission bits only
+  ASSERT_THAT(st.st_mode & 0777, Eq(mode));
+
+  std::remove(TemporaryFilePath());
+}
+
 TEST(TestRadsanInterceptors, CreatDiesWhenRealtime) {
   auto Func = []() { creat(TemporaryFilePath(), S_IWOTH | S_IROTH); };
   ExpectRealtimeDeath(Func, "creat");
@@ -217,6 +233,28 @@ TEST(TestRadsanInterceptors, FcntlDiesWhenRealtime) {
   ExpectNonRealtimeSurvival(Func);
 }
 
+TEST(TestRadsanInterceptors, FcntlFlockDiesWhenRealtime) {
+  int fd = creat(TemporaryFilePath(), S_IRUSR | S_IWUSR);
+  ASSERT_THAT(fd, Ne(-1));
+
+  auto func = [fd]() {
+    struct flock lock {};
+    lock.l_type = F_RDLCK;
+    lock.l_whence = SEEK_SET;
+    lock.l_start = 0;
+    lock.l_len = 0;
+    lock.l_pid = ::getpid();
+
+    ASSERT_THAT(fcntl(fd, F_GETLK, &lock), Eq(0));
+    ASSERT_THAT(lock.l_type, F_UNLCK);
+  };
+  ExpectRealtimeDeath(func, "fcntl");
+  ExpectNonRealtimeSurvival(func);
+
+  close(fd);
+  std::remove(TemporaryFilePath());
+}
+
 TEST(TestRadsanInterceptors, CloseDiesWhenRealtime) {
   auto Func = []() { close(0); };
   expectRealtimeDeath(Func, "close");